Travelling worktable apparatus

ABSTRACT

In a travelling worktable apparatus including a roller guide unit to guide a travelling table. Deformation of a sample table caused in association with precision of the guide unit such as deviation in precision of rail attachment and precision of rollers is prevented while keeping rigidity of the roller guide. This keeps a fixed distance between a bar mirror unit and a sample on the sample table. For this purpose, the Y table (top table) of the prior art is subdivided into a travelling table to hold the roller guide and a sample table to mount a sample thereon. These tables are fixed by a pin which can be more easily deformed than the tables and are linked with each other by an elastic body.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a travelling worktable apparatus(a sample travelling worktable apparatus or a sample stage apparatus)for semi-conductor manufacturing apparatuses, semiconductor inspectingapparatuses, and working tools to achieve fine machining with highprecision, and in particular, to improvement of measurement errors inmeasurement of a position of a sample.

[0003] 2. Description of the Related Art

[0004] In general, in semiconductor manufacturing apparatuses and/orsemiconductor inspecting apparatuses, a travelling stage apparatus(travelling worktable apparatus) to transport a sample such as a wafermust have a positioning function with high precision. Therefore, a laserfor high-precision measurement is usually employed to detect a sampleposition. In such a configuration, a position of a mirror placed on asample table is measured by a laser to control the sample position. Inthe detection of the sample position according to values measured by alaser, variation in distance between the mirror (bar mirror) and thesample has been heretofore neglected. However, in an apparatus whichrequires higher precision in the positioning of a sample, the distancebetween the bar mirror and the sample varies by deformation of the tablecaused by a guide apparatus, for example, deviation in precision ofrollers used in the guide apparatus and precision in attachment of theguide apparatus. It is consequently difficult to control the sampleposition with high precision.

[0005] Referring to FIGS. 1 and 2, description will be given of theproblem for easy understanding of the gist of the problem.

[0006] First, description will be given of a configuration of a generaltravelling table apparatus of FIG. 1 and a measuring method of theapparatus.

[0007] The configuration of FIG. 1 includes a top table 1 which cantravel in an x-axis direction and in a y-axis direction, an X bar mirror5 for x-directional measurement, and a Y bar mirror 6 for y-directionalmeasurement. A sample 30 is placed on the top table 1. It is necessaryto keep the sample 30 at the position when the top table 1 is moved.Therefore, the sample is adsorbed onto the top table 1 using vacuum orelectrostatic force or is mechanically fixed thereon. First, thex-directional measurement will be described. Laser emitted from a laserhead 10 is split by a beam splitter 9. Resultant light proceeds via aninter-ferometer 7 in a direction vertical to the X bar mirror 5.Reflected light from the mirror 5 again passes through theinterferometer 7 (the light again reflects on the mirror 5 in adouble-path system). There is obtained interference light. The light isthen received by a receiver 8. The receiver 8 accordingly produces asignal indicating a position of the mirror 5. Also in the y-axisdirection, the distance between the interferometer 7 and the Y barmirror 6 can be detected in a similar way. If the distance between thesample and each of the bar mirrors is kept unchanged, the sampleposition can be controlled with high precision according to variation inthe distance of each bar mirror.

[0008] However, when the top table 1 is deformed as shown in FIG. 2,distance between a center of the sample 30 on the top table 1 and themirror for x-directional measurement increases by ΔX relative tooriginal distance X therebetween. An error of ΔX appears in a measuredvalue of distance, and hence the sample positioning precision islowered.

[0009] JP-A-1-274936 describes a prior art example of a travelling stage(X-Y stage). In the configuration of the travelling stage, springs areinserted respectively in a pressurized section and a fixing section of aguide rail so that the guide rail frees deformation of the table causedin association with the precision of the guide apparatus described aboveor by variation in temperature and a thermal expansion coefficient.

[0010]FIG. 11 shows the freeing structure of the guide rail in the priorart example in a schematic diagram.

[0011] In the configuration shown in FIG. 11, a coned disc spring 85 isdisposed on a support pin 83 of a guide rail 82 on pressurized side, theguide rail being attached onto a travelling table 80. Compressive forceof the spring 85 brings the guide rail 82 into tight contact with thetravelling table 80. This allows a degree of freedom for the guide rail82 with respect to variation in pressure beforehand applied on thepressurized side. Also in the pressurized section, a compression spring87 is arranged for a pressure pin 89 to keep the pressure of the guideapparatus at a predetermined level. This also contributes to suppressdeformation of the table 80.

[0012] In the configuration of the prior art example, the spring 85 isused to bring the guide rail 82 into tight contact with the travellingtable 80. The guide rail 82 on the pressurized side has a degree offreedom also in other than the pressurized direction.

[0013] In other words, movement of the table 80 in a direction verticalto an upper surface of the table 80 depends on compressive force of thespring 85. Therefore, when there appears acceleration due to shock orvibration in the vertical direction, the upper surface of the table 80easily becomes unstable. To overcome this difficulty, if it is desiredto increase rigidity of the table 80 in the vertical direction, thespring 85 must have a larger spring modulus. However, to guarantee theoriginal purpose, namely, the smooth shift toward the pressurizeddirection, frictional force on the attaching surface must be minimized.

[0014] For this purpose, it can be considered a method to reduceroughness of the attaching surface, namely, to smooth the surface like amirror surface. However, in consideration of the overall travellingtable, since rigidity of the table in the travelling direction is as lowas that in the pressurized direction, the structure becomes weak withrespect to self-excited vibration and/or external disturbance.

SUMMARY OF THE INVENTION

[0015] It is therefore an object of the present invention to provide atravelling worktable apparatus in which deformation of the guideapparatus is reduced to a low level while keeping rigidity of the guideapparatus such that the distance between the mirror and a sample placedon the upper surface of the table can be kept fixed.

[0016] In accordance with the present invention, there is provided atravelling worktable apparatus, comprising a fixed base,an intermediatetable mounted on said fixed base with a first guide disposedthere-between, said intermediate table being capable of achieving areciprocating motion, a top table mounted on said intermediate tablewith a second guide disposed therebetween, said top table being capableof achieving a reciprocating motion in a direction which intersects adirection of the reciprocating motion of said inter-mediate table; and ameasuring mirror disposed on said top table. The top table comprises atravelling table for holding said second guide, a sample table disposedon said travelling table for mounting a sample thereon, a pin forrestricting said travelling table and said sample table, said pin beingmore easily deformed than said travelling table and said sample table;and an elastic body disposed between said travelling table and saidsample table.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The objects and features of the present invention will becomemore apparent from the consideration of the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

[0018]FIG. 1 is a plan view showing an overall configuration of ageneral travelling worktable apparatus;

[0019]FIG. 2 is a side view showing a variation of a table in thetravelling worktable apparatus shown in FIG. 1;

[0020]FIG. 3A is a plan view showing an embodiment of a travellingworktable apparatus according to the present invention;

[0021]FIG. 3B is a side view showing an embodiment of a travellingworktable apparatus according to the present invention;

[0022]FIG. 4 is a magnified view of section A of FIG. 3A;

[0023]FIG. 5 is a side view to explain the embodiments shown in FIGS. 3Aand 3B;

[0024]FIG. 6 is a perspective view to explain the embodiments shown inFIGS. 3A and 3B;

[0025]FIG. 7 is a perspective view of a parallel plate spring in anotherembodiment according to the present invention;

[0026]FIG. 8 is a side view to explain action of the plate spring shownin FIG. 7;

[0027]FIG. 9 is a side view of a sample table and a travelling table inanother embodiment according to the present invention;

[0028]FIG. 10A is a plan view showing a sample table and a travellingtable in another embodiment according to the present invention;

[0029]FIG. 10B is a cross-sectional diagram showing a sample table and atravelling table in another embodiment according to the presentinvention; and

[0030]FIG. 11 is a magnified cross-sectional diagram showing part of asample table and part of a travelling table in a prior art example.

DETAILED DESCRIPTION

[0031] Referring now to the drawings, description will be given of anembodiment according to the present invention.

[0032] First, description will be given of embodiments shown in FIGS.3A, 3B, 4, and 5.

[0033]FIGS. 3A, 3B, and 4 are a plan view of a travelling worktableapparatus, a side view thereof, and a magnified view of section A ofFIG. 3A, respectively.

[0034] In FIGS. 3A and 3B, an X table (intermediate table) 2 is mountedon a fixed base 3 with a roller guide unit 11 disposed therebetween. A Ytable (top table) 1 is mounted on a intermediate table 2 with a rollerguide unit 12 disposed therebetween. The top table 1 is constituted witha Y1 table (travelling table) 20 to support a guide apparatus and a Y2table (sample table) 21 to mount a sample and a mirror. Tables 20 and 21are coupled with each other by a parallel plate spring 25 which easilydeforms in the X-axis and Y-axis directions. In the mounting of thetables 2 and 1, a pressure screw 15 pressurizes a pressurized-side guiderail 11A2 attached on the fixed-side table and a pressurized-side guiderail 12A2. Details of the roller guide units will be described byreferring to FIGS. 3A, 3B, and 4. Since the roller guide units 11 and 12are of the same mechanism, description will be given of only thepressure side of the roller guide 12.

[0035]FIG. 4 is a magnified plan view of section A of FIG. 3A. Theroller guide unit 12 includes two guide rails 12B1 and 12B2 disposed ona rear surface of the Y table 1 in the Y-axis direction, two guide rails12A1 and 12A2 disposed corresponding to the guide rails 12B1 and 12B2 onthe X table 2 in the Y-axis direction, a retainer 12C with a roller 12Darranged between the guide rails, and a pressure screw 15 to applythrust to bring the roller 12D into tight contact with its opposingguide rail.

[0036] The roller guide unit 12 is of a crossed roller type in whichmany rollers 12D are arranged on the retainer 12C in a cross layout,namely, the rollers 12D alternately changes its direction by 90°. Therollers 12D are held by the retainer 12C in a movable state. That is,the rollers 12D are brought into contact with grooves with a V-shapedcross section respectively disposed in opposing surfaces of the guiderails 12A2 and 12B2 and rolls thereon keeping the contact on thegrooves.

[0037] Advantages of the embodiment will be described by referring toFIGS. 5 and 6.

[0038] When the guide rail 12A2 is pressurized, if a diameter of theroller 12D1 held between the guide rails 12A2 and 12B2 and between guiderails 12A1 and 12B1 (FIG. 4) is smaller than a diameter of the roller12D2 which is going to enter a space between the guide rails for tabletransportation, force is upward applied in an inclined direction betweenthe guide rails due to the direction of the roller 12D2 in FIGS. 5 and6. The Y1 table 20 is resultantly deformed. However, the deformation isabsorbed by the spring 25 disposed between the Y1 table 20 and the Y2table 21, and hence the deformation of the Y2 table 21 is reduced. Next,the roller 12D3 to enter the space between the guide rails (FIG. 4) ischanged in direction by 90° relative to the roller 12D2. Therefore, theY1 table 20 receives force downward in an inclined direction. However,the deformation of the sample table 21 is minimized as described above.In this connection, similar advantage can be expected for deformation ofthe tables caused by attaching errors of the guide rails and/ordeformation of the tables due to variation in temperature.

[0039] By disposing an absorber 50 between the sample table 21 and thetravelling table 20, vibration of the Y2 table 21 can be controlled. Itis therefore possible to mitigate influence of reduction of rigidity dueto an elastic body or element. There may be employed a mechanicalabsorber employing air, fluid, and the like as well as materials havingvibration preventing effect such as synthetic resin, lubber, and thelike.

[0040] When a degree of freedom exists between the Y1 table 20 and theY2 table 21, the position of the Y2 table 21 relative to the Y1 table 20is easily changed. In the positioning of a sample, this elongates aperiod of time to determine a position of the Y2 table 21 byacceleration or deceleration. To overcome the difficulty, a part of theY1 table 20 and a part of the Y2 table 21 are restricted by a pin 40having rigidity lower than that of the Y1 table 20 and the Y2 table 21as shown in FIG. 6 to thereby remove translational motion of the Y2table 21. Additionally, a parallel plate spring 25 including platespring members 61 and 62 which can be easily deformed in one directionas shown in FIGS. 7 and 8 is attached with the deforming directions ofthe respective members 61 and 62 respectively matching the X-axis andY-axis direction. This configuration prevents rotary motion of the Y2table 21.

[0041] Description will now be given of another embodiment shown inFIGS. 7 and 8.

[0042] This embodiment is a parallel plate spring which can absorbdeformation of the travelling table.

[0043] The parallel plate spring includes a Y1 table attaching member60, a plate spring member 61 which can easily deform in the Y-directionof FIG. 7, a plate spring member 62 which is disposed on the member 61and which can easily deform in the X-direction of FIG. 7, and a Y2 tableattaching member 63. The spring members 61 and 62 easily deform in thedirections which are substantially orthogonal to each other. Therefore,even when deformation containing X-directional and Y-directionalcomponents takes place in the travelling table, the deformation can beabsorbed by the spring members 61 and 62. FIG. 8 shows a state of thespring member 62 when the parallel plate spring is deformed. As can beseen from FIG. 8, the spring is changed in height by the deformation.Variation of the height can be obtained using an expression as follows.

ΔZ=L(l−cosθ); θ=sin⁻¹ (A/L)

[0044] where, ΔZ is displacement in a Z-axis direction of Y2 attachingmember, L is length of the plate spring member, and A is relativedisplacement between Y1 table attaching member and Y2 table attachingmember.

[0045] Assume that the plate spring member has a height of 10millimeters (mm) and the relative displacement between the Y1 tableattaching member and the Y2 table attaching member is one micrometer(μm). Then, the displacement ΔZ in the Z-axis direction can beconsiderably minimized as

[0046] ΔZ=0.05 nanometer (nm).

[0047] Next, description will be given of another embodiment shown inFIG. 9.

[0048] In this embodiment, a parallel plate spring is not used as theelastic member or unit.

[0049] As shown in FIG. 9, in a configuration in which the Y2 table 21is linked with the Y1 table 20 by a bolt 70 with a spacer 65 between thetables 21 and 20, when an elastic modulus of the Y2 table 21 is largethan that of the bolt 70, the bolt 70 serves as the elastic member. Thatis, deformation of the Y2 table 21 can be absorbed by the bolt 70. Assuch a combination, when the Y2 table 21 is made of ceramics and thebolt 70 is made of phosphor bronze, the advantage is enhanced.Advantageous absorption of the deformation can also be achieved byincreasing the number of bolts and by reducing the diameter of thebolts.

[0050] Subsequently, another embodiment shown in FIGS. 10A and 10B willbe described.

[0051]FIG. 10A is a plan view of the sample table and the travellingtable and FIG. 10B is a cross-sectional view along line C-C of FIG. 10A.

[0052] This example is associated with a travelling worktable apparatus.In the apparatus, a travelling table includes a part which can be easilydeformed, and deformation in linking part between the travelling tableand the sample table is minimized.

[0053] In the configuration, the Y1 table 20 is directly linked with theY2 table 21 by the bolt 70. In this state, only a central area of the Y1table 20 is brought contact with a central area of the Y2 table 21. Asshown in FIG. 10B, a groove is formed in the Y1 table 20. The Y1 table20 is therefore easily deformed in an area near the groove. The centralpart of the Y1 table 20 in contact with the Y2 table 21 is configuredsuch that deformation of the guide retaining section is not easilypropagated. When compared with the second embodiment not using theparallel plate spring, this embodiment is more effective to reducedeformation of the sample table. Additionally, the elastic member isformed integrally in the Y2 table, the number of parts can be reducedand the size of the apparatus can be efficiently minimized.

[0054] In accordance with the present invention, the deformation of thetables is minimized while keeping rigidity of the guide apparatus.Therefore, the distance between the mirror and the sample on the uppersurface of the table can be kept fixed.

[0055] While the present invention has been described in detail andpictorially in the accompanying drawings, it is not limited to suchdetails since many changes and modifications recognizable to those ofordinary skill in the art may be made to the invention without departingfrom the spirit and scope thereof.

1. A travelling worktable apparatus, comprising: a fixed base; anintermediate table mounted on said fixed base with a first guidedisposed therebetween, said intermediate table being capable ofachieving a reciprocating motion; a top table mounted on saidintermediate table with a second guide disposed therebetween, said toptable being capable of achieving a reciprocating motion in a directionwhich intersects a direction of the reciprocating motion of saidintermediate table; and a measuring mirror disposed on said top table,wherein said top table comprises: a travelling table for holding saidsecond guide; and a sample table disposed on said travelling table formounting a sample thereon, said travelling table and said sample tablebeing linked with each other at central portions respectively thereof,said travelling table having a groove, said groove facilitatingdeformation of said travelling table.